Process for producing aqueous resin dispersion

ABSTRACT

This invention provides a process for producing an aqueous resin dispersion in which the average particle diameter of the dispersed resin is not more than 500 nm, comprising finely dispersing a monomeric mixture (I) containing (A) fatty acid-modified polymerizable unsaturated monomer and (B) other polymerizable unsaturated monomer which is copolymerizable with the monomer (A) in an aqueous medium in such a manner that the dispersed particles have an average particle diameter not more than 500 nm, and polymerizing the resulting emulsified product. The invention also provides aqueous resin compositions which comprise the aqueous resin dispersions, and water-based paint compositions which comprise the aqueous resin compositions.

TECHNICAL FIELD

This invention relates to a process for producing aqueous resindispersions which can form coating film of excellent drying propertywith both thick appearance and high gloss; aqueous resin compositionswhich contain the aqueous resin dispersions; and water-based paintcompositions which contain the aqueous resin compositions.

BACKGROUND ART

Recently shift from organic solvent-based compositions to water-basedcompositions in the art of paint, ink, adhesive and the like is underprogress, for conservation of natural resources, environmentalsanitation, prevention of pollution and provision of non-dangerousproducts. For example, as vehicles used in water-based paintcompositions, for example, resins such as alkyd resin, acrylic resin,polyester resin, polyurethane resin, epoxy resin and the like can benamed. When unsaturated fatty acid is used as a starting material ofalkyd resin, oxidation-hardenable groups can be introduced into theresin's skeletal structure, and when such alkyd resin is used as avehicle of water-based paint compositions, the compositions can beone-liquid cold set. Also due to oiliness of the resin, the water-basedpaint compositions are expected to exhibit anti-corrosive effect whenthey are applied onto metallic surfaces. The resin's softness, however,retards drying of the coated film, which generally results in lowweatherability. On the other hand, acrylic resin is quick-drying andhighly weather-resistant but is inferior in corrosion resistance. As aresinous material for the aqueous system which concurrently exhibits thecharacteristic properties of these two kinds of resins, graft resinsformed by binding alkyd resins and acrylic resins by chemical reactionhave been developed and many proposals were made. For example, JP Sho 50(1975)-126723A, JP Sho 56 (1981)-5863A and Sho 60 (1985)-221469Adisclosed a method for producing aqueous solutions or dispersions ofsuch resins, which comprised making a fatty acid-modified monomerthrough reaction of unsaturated fatty acid having non-conjugated doublebond with glycidyl ester of α,β-ethylenically unsaturated acid,copolymerizing the fatty acid-modified monomer with unsaturated monomersuch as α,β-ethylenically unsaturated carboxylic acid in organicsolvent, neutralizing the carboxyl groups in the resulting resin withbasic substance, and thereafter diluting the resin with water. However,those hydrophilic resins according to the method are prepared throughsolution polymerization, and the formed polymers must be dissolved inorganic solvent. Hence it is generally difficult to give them highmolecular weight. Furthermore, for dissolving or dispersing the formedpolymers in water, monomers having hydrophilic groups such as carboxylor hydroxyl groups, or an emulsifier must be used in large quantities.In consequence, coating films formed of the polymers are subject to aproblem of insufficient water resistance.

JP Sho 59 (1984)-8773A disclosed preparation of an oxidativepolymerization type aqueous emulsion by emulsion polymerization of aradical-polymerizable monomeric mixture using a surfactant and/or highmolecular protective colloid. The monomeric mixture contained a fattyacid-modified monomer which was obtained through a reaction of a dryingoil fatty acid or semi-drying oil fatty acid with glycidyl ester ofα,β-etylenically unsaturated acid.

The formation mechanism of an emulsion polymer is such that theparticipating monomer(s) diffuse in water from large monomer dropspresent in the aqueous phase, and the polymerization progresses in themicelles formed by surfactant, to produce polymer particles (smallparticles under polymerization). In that occasion, the monomer(s) usedfor the polymerization must be supplied under the polymerizationconditions, from the monomer drops to the polymer particles, as theydiffuse and migrate in the water.

There are generally large differences in particle diameter between themonomer drops and the polymer particles growing from the micelles. Thismeans there is large difference between the total surface area of themonomer drops and that of the polymer particles, and therefore initiatorradicals or the monomer(s) diffusing in the water penetrate into thoseof the greater surface area, i.e., into the polymer particles and thepolymerization progresses in situ. During the emulsion polymerization,the polymer particles grow as their diameters gradually increase.

In the occasion of emulsion polymerizing the radical-polymerizablemixture containing the fatty acid-modified monomer, the fattyacid-modified monomer having a very low water-solubility is left in themonomer drops at the polymerization stage, and the polymerizationprogresses in the monomer drops, producing polymer particles containingmany of the fatty acid-modified monomer units. On the other hand, themonomer(s) other than the fatty acid-modified monomer diffuse in thewater from the monomer drops into the micelles to form polymer particlescontaining many units of the monomer(s) other than the fattyacid-modified monomer. Thus, in high probability drastically irregulardistribution of hydrophilic polymer particles and hydrophobic polymerparticles occurs in the finally obtained emulsion. In consequence,coating films formed from above-described oxidative polymerization typeaqueous emulsions have such problems that the hydrophobic polymerparticles provide nuclei to cause cissing, or they come up to thesurface to retain tackiness at the surface, or due to theirincompatibility transparent film cannot be obtained to markedly impairappearance of the finished coating film.

As a measure to overcome those problems as above, EP-A-1044993 proposedaqueous copolymers containing a copolymer which was a polymerizationproduct of vinyl monomers and a hydrophobic ester or partial ester, andtheir production process. The publication proposed addition of ahydrophobic ester from drying oil acid and polyol to the monomer dropsat the polymerization time, to inhibit formation of second generationparticles other than the monomer drops. The aqueous copolymers that aredescribed in the publication do not contain volatile fusion assistantand form transparent film, but they are slow drying particularly at theinitial stage after application. In actual use the coating film from thecopolymers retains tackiness. The coating film is also subject to suchdefects that its weatherability and water resistance are insufficient.

DISCLOSURE OF THE INVENTION

The main object of the present invention is to provide a process forstably producing an aqueous resin dispersion by emulsion polymerizationof a monomeric mixture containing a fatty acid-modified polymerizableunsaturated monomer or monomers, and other polymerizable unsaturatedmonomer or monomers which are copolymerizable therewith.

We have engaged in concentrative studies for accomplishing the aboveobject, and now discovered that an aqueous resin composition whichexhibits both polymerization stability and storage stability and whichforms coating film having excellent water resistance, weatherability andso an can be obtained by a process comprising finely dispersing amonomeric mixture containing a fatty acid-modified polymerizablemonomer(s), such that a specific average particle diameter is attained,and polymerizing the resulting monomeric emulsified product. Still morepreferably, as the monomeric emulsified product, one of specificmonomeric composition is selected. The present invention is whereuponcompleted.

Thus, the present invention provides a process for producing an aqueousresin dispersion in which the average particle diameter of the dispersedresin is not more than 500 nm, comprising finely dispersing a monomericmixture (I) containing (A) fatty acid-modified polymerizable unsaturatedmonomer and (B) other polymerizable unsaturated monomer which iscopolymerizable with the monomer (A) in an aqueous medium in such amanner that the dispersed particles have an average particle diameternot more than 500 nm, and polymerizing the resulting emulsified product,or mini-emulsion polymerizing the same.

The present invention also provides aqueous resin compositions whichcontain said aqueous resin dispersion, and water-based paintcompositions which contain said aqueous resin compositions.

According to the above process of this invention, an aqueous resindispersion containing fatty acid-modified monomer units can be stablyprepared, without using a large quantity of organic solvent or auxiliarysurfactant and the like. Furthermore, aqueous resin compositions andwater-based paint compositions which contain the aqueous resindispersion show excellent storage stability and film-forming ability.They can be readily hardened at ambient temperature although they aresingle-component type and still in addition, hardened coating filmsformed therefrom have very favorable transparency, gloss and appearance(thick appearance), and show excellent performances in water resistance,durability, corrosion resistance, weatherability and the like. Thus, thepresent invention achieves conspicuous effects. In particular, thewater-based paint compositions which contain the aqueous resindispersion are suitable for protective coating on metallic surfaces,because they are well compatible with metallic surfaces such as of ironand can prevent occurrence of rust spots or the like.

Hereafter the present invention is explained in further details.

The process of the present invention is characterized in that itcomprises finely dispersing a monomeric mixture (I) which contains (A)fatty acid-modified polymerizable unsaturated monomer(s) and (B) otherpolymerizable unsaturated monomer(s) which are copolymerizable with themonomer (A) in an aqueous medium such that the average particle diameterbecomes no more than 500 nm, and polymerizing the resulting monomericemulsified product, or mini-emulsion polymerizing the same.

Where the average particle diameter of the monomeric mixture in theemulsified product exceeds 500 nm, sedimentation of the monomericemulsified product during storage or heterogeneity inhydrophilic-hydrophobic components' distribution become notable. Thosephenomena are apt to cause opacity in coating film formed of thecompositions prepared from the product and hence are undesirable.

In the present specification, the average particle diameter is measuredof a sample diluted with deionized water, with SALD-3100™ (ShimazuSeisakujo, a laser diffraction particle size distribution measuringapparatus) at ambient temperature (around 20° C.). The average particlediameter is measured within 24 hours of the preparation of sampleemulsified product of finely divided monomers or aqueous resindispersion.

As the aqueous medium used at the polymerization time, water orwater-organic solvent mixed solution prepared by mixing an organicsolvent such as a water-soluble organic solvent with water which is thechief component, can be named.

Fatty Acid-Modified Polymerizable Unsaturated Monomer (A)

In the present invention, fatty acid-modified polymerizable unsaturatedmonomer (A) is used for facilitating fine granulation (ormini-emulsification) of the monomeric mixture at the time of itsemulsification; for stabilizing the monomeric emulsified product afterthe fine granulation at its polymerization stage and inhibitingdiffusion of other polymerizable unsaturated monomer (B) into theaqueous medium; for imparting thick appearance to the coating filmformed by using the particles dispersed in the aqueous resin dispersionas prepared in the above-described manner; and for introducingoxidation-hardenable groups into the particles dispersed in the aqueousresin dispersion. The monomer includes polymerizable unsaturatedmonomers having polymerizable unsaturated groups at terminals ofhydrocarbon chains derived from fatty acid. As the polymerizableunsaturated groups herein referred to, for example, vinyl group,(meth)acryloyl groups and the like can be named, meth(acryloyl) groupsbeing particularly preferred.

As the fatty acid-modified polymerizable unsaturated monomer (A), forexample, those which can be obtained by reacting fatty acid (a1) withepoxy-containing polymerizable unsaturated monomer (a2) orhydroxyl-containing polymerizable unsaturated monomer (a3) can be used.

As the fatty acid (a1), those having a structure that a carboxyl groupis bound to one end of hydrocarbon chain, for example, drying oil fattyacid, semi-drying oil fatty acid and non-drying oil fatty acid can benamed. While drying oil fatty acid and semi-drying oil fatty acid arenot strictly distinguishable, normally drying oil fatty acid is anunsaturated fatty acid having iodine value no less than 130, andsemi-drying oil fatty acid is an unsaturated fatty acid having iodinevalue of at least 100 but less than 130. On the other hand, non-dryingoil fatty acid normally has iodine value less than 100.

As the drying oil fatty acid and semi-drying oil fatty acid, forexample, fish oil fatty acid, dehydrated caster oil fatty acid,safflower oil fatty acid, linseed oil fatty acid, soybean oil fattyacid, sesame oil fatty acid, poppy oil fatty acid, perilla oil fattyacid, hempseed oil fatty acid, grape kernel oil fatty acid, corn oilfatty acid, tall oil fatty acid, sunflower oil fatty acid, cottonseedoil fatty acid, walnut oil fatty acid, rubber seed oil fatty acid,highly conjugated dehydrated caster oil fatty acid and the like can benamed. As the non-drying oil fatty acid, for example, coconut oil fattyacid, hydrogenated coconut oil fatty acid, palm oil fatty acid and thelike can be named. These can be used either singly or in combination oftwo or more. Furthermore, these fatty acids can be concurrently usedwith caproic acid, capric acid, lauric acid, myristic acid, palmiticacid, stearic acid and the like.

The epoxy-containing polymerizable unsaturated monomer (a2) which isreactable with above fatty acid (a1) for preparing the fattyacid-modified polymerizable unsaturated monomer (A) includes compoundshaving one epoxy group and one polymerizable unsaturated group permolecule. More specifically, for example, glycidyl meth(acrylate),β-methylglycidyl meth(acrylate), 3,4-epoxycyclohexylmethylmeth(acrylate), 3,4-epoxycyclohexylethyl meth(acrylate),3,4-epoxycyclohexylpropyl meth(acrylate), allylglycidyl ether and thelike can be named. These can be used either singly or in combination oftwo or more.

The fatty acid (a1) and epoxy-containing polymerizable unsaturatedmonomer (a2) can be reacted at such ratios that the equivalent ratiobetween carboxyl groups in the fatty acid (a1) and epoxy groups in theepoxy-containing monomer (a2) lies within a range of 0.75:1-1.25:1,preferably 0.8:1-1.2:1.

The reaction of above fatty acid (a1) with the epoxy-containingpolymerizable unsaturated monomer (a2) is normally conducted in thepresence of a polymerization inhibitor under such conditions as will notinduce problems in the reaction such as gelation but allow smoothreaction of carboxyl groups in the fatty acid component with epoxygroups in the epoxy-containing polymerizable unsaturated monomer. It isnormally suitable to conduct the reaction by heating at temperatures ofabout 100-about 180° C. for about 0.5-about 10 hours.

For the reaction an esterification catalyst such as tertiary amine,e.g., N,N-dimethylaminoethanol and the like, or quaternary ammoniumsalt, e.g., brominated tetraethylammonium, brominated tetrabutylammoniumand the like can be used. Furthermore, an organic solvent which is inertto the reaction can be used.

As the polymerization inhibitor, those per se known radicalpolymerization inhibitors, for example, hydroxy compound such ashydroquinone, hydroquinone monomethyl ether, pyrocatechol,p-tert-butylcatechol and the like; nitro compound such as nitrobenzene,nitrobenzoic acid, o-, m- or p-dinitrobenzene, 2,4-dinitrotoluene,2,4-dinitrophenol, trinitrobenzene, picric acid and the like; quinonecompound such as p-benzoquinone, dichlorobenzoquinone, chloranil,anthraquinone, phenanthroquinone and the like; and nitroso compound suchas nitrosobenzene, nitroso-β-naphthol and the like can be named. Thesecan be used either singly or in combination of two or more.

The fatty acid-modified polymerizable monomer (A) can also be obtainedthrough esterification reaction of said fatty acid (a1) withhydroxyl-containing polymerizable unsaturated monomer (a3). Thehydroxyl-containing polymerizable unsaturated monomer (a3) includesthose compounds having one hydroxyl group and one polymerizableunsaturated group per molecule, more specifically, for example, C₂-C₈hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl meth(acrylate),2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate,hydroxybutyl (meth)acrylate and the like; allyl alcohol; (meth)acrylateshaving hydroxyl group such as α-caprolactone-modified products of aboveC₂-C₈ hydroxyalkyl (meth)acrylates; and (meth)acrylates havingpolyoxyethylene chain having a hydroxyl group at its molecular end.These may be used either singly or in combination of two or more.

The fatty acid (a1) and hydroxyl-containig polymerizable unsaturatedmonomer (a3) can be normally reacted at such ratios that the equivalentratio of carboxyl groups in the fatty acid (a1) to hydroxyl groups inthe hydroxyl-containing monomer (a3) lies within a range of0.4:1-1.25:1, preferably 0.5:1-1.2:1.

The reaction of the fatty acid (a1) with the hydroxyl-containingpolymerizable unsaturated monomer (a3) is normally conducted in thepresence of a polymerization inhibitor under such conditions as will notinduce problems such as gelation but allow smooth reaction of carboxylgroups in the fatty acid component with hydroxyl groups in thehydroxyl-containing polymerizable unsaturated monomer. It is normallysuitable to conduct the reaction in the presence of an esterificationcatalyst, by heating at temperatures of about 100-about 180° C., forabout 0.5-about 10 hours. As the esterification catalyst, for example,sulfuric acid, aluminium sulfate, potassium hydrogensulfate,alkyl-substituted benzene, hydrochloric acid, methyl sulfate, phosphoricacid and the like can be named. These catalysts can be used normallywithin a range of about 0.001-about 2.0 wt % to the combined amount ofthe fatty acid (a1) and hydroxyl-containing polymerizable unsaturatedmonomer (a3) that are reacted. Furthermore, an organic solvent which isinert to the reaction may be used.

As the polymerization inhibitor, those per se known radicalpolymerization inhibitors, for example, hydroxy compound such ashydroquinone, hydroquinone monomethyl ether, pyrocatechol,p-tert-butylcatechol and the like; nitro compound such as nitrobenzene,nitrobenzoic acid, o-, m- or p-dinitrobenzene, 2,4-dinitrotoluene,2,4-dinitrophenol, trinitrobenzene, picric acid and the like; quinonecompound such as p-benzoquinone, dichlorobenzoquinone, chloranil,anthraquinone, phenanthroquinone and the like; and nitroso compound suchas nitrosobenzene, nitroso-β-naphthol and the like can be named. Thesecan be used either singly or in combination of two or more.

Other Polymerizable Unsaturated Monomer (B)

The other polymerizable unsaturated monomer (B) which is used in theprocess of the present invention signifies those polymerizableunsaturated monomers which are copolymerizable with above fattyacid-modified polymerizable unsaturated monomer (A), and includes suchcompounds which contain at least one, preferably one only, polymerizableunsaturated group per molecule, e.g., vinyl group, (meth)acryloyl groupand the like.

As specific examples of such other polymerizable unsaturated monomer(B), alkyl or cycloalkyl (meth)acrylates such as methyl (meth)acrylate,ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate,n-butyl (meth)acrylate, i-butyl (meth)acrylate, tert-butyl(meth)acrylate, n-hexyl (meth)acrylate, octyl (meth)acrylate,2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, tridecyl(meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate,isostearyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl(meth)acrylate, t-butylcyclohexyl (meth)acrylate, cyclododecyl(meth)acrylate, and the like; polymerizable unsaturated compounds havingisobornyl group such as isobornyl (meth)acrylate; polymerizableunsaturated compounds having adamantyl group such as adamantyl(meth)acrylate; vinyl aromatic compounds such as styrene,α-methylstyrene, vinyltoluene and the like; polymerizable unsaturatedcompounds having alkoxysilyl group such as vinyl trimethoxysilane, vinyltriethoxysilane, vinyl tris (2-methoxyethoxy) silane,γ-(meth)acryloyloxypropyl-trimethoxysilane,γ-(meth)acryloyloxypropyl-triethoxysilane and the like; perfluoroalkyl(meth)acrylates such as perfluorobutylehtyl (meth)acrylate,perfluorooctylethyl(meth)acrylate and the like; polymerizableunsaturated compounds having photopolymerizable functional group likemaleimide group; 1,2,2,6,6,-pentamethylpiperidyl (meth)acrylate,2,2,6,6,-tetramethylpiperidinyl (meth)acrylate and the like; vinylcompounds such as N-vinylpyrrolidone, ethylene, butadiene, chloroprene,vinyl propionate, vinyl acetate and the like; compounds having carboxylgroup such as (meth)acrylic acid, maleic acid, crotonic acid,β-carboxyethyl acrylate and the like; nitrogen-containing polymerizableunsaturated compounds such as (meth)acrylonitrile, (meth)acrylamide,dimethylaminopropyl (meth)acrylamide, dimethylaminoethyl (meth)acrylate,adducts of glycidyl (meth)acrylate and amines, and the like; C₂-C₈hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl meth(acrylate),2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate,hydroxybutyl (meth)acrylate and the like; allyl alcohol; (meth)acrylateshaving hydroxyl group such as ε-caprolactone-modified products of aboveC₂-C₈ hydroxyalkyl (meth)acrylates; polymerizable unsaturated compoundshaving hydroxyl group such as (meth)acrylates having polyoxyethylenechain having a hydroxyl group at its molecular end; (meth)acrylateshaving polyoxyethylene chain having an alkoxy group at its molecularend; polymerizable unsaturated compounds having sulfonic acid group suchas 2-acrylamide-2-methylpropanesulfonic acid, allylsulfonic acid, sodiumstyrenesulfonate, sulfoethyl methacrylate and sodium salt or ammoniumsalt thereof; addition reaction products of hydroxybenzophenones withglycidyl (meth)acrylate, examples of the hydroxybenzophenone including2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone,2-hydroxy-4-(3-acryloyloxy-2-hydroxypropoxy)benzophenone,2,2′-dihydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone,2,2′-dihydroxy-4-(3-acryloyloxy-2-hydroxypropoxy)benzophenone and thelike, or polymerizable unsaturated compounds havingultraviolet-absorbing functional group such as2-(2′-hydroxy-5′-methacryloyloxyethylphenyl)-2H-benzotriazole or thelike; ultraviolet-stable polymerizable unsaturated compounds such as4-(meth)acryloyloxy-1,2,2,6,6,-pentamethylpiperidine,4-(meth)acryloyloxy-2,2,6,6,-tetramethylpiperidine,4-cyano-4-(meth)acryloylamino-2,2,6,6,-tetramethylpiperidine,1-(meth)acryloyl-4-(meth)acryloylamino-2,2,6,6,-tetramethylpiperidine,1-(meth)acryloyl-4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine,4-crotonoyloxy-2,2,6,6,-tetramethylpiperidine,4-crotonoylamino-2,2,6,6,-tetrametylpiperidine,1-crotonoyl-4-crotonoyloxy-2,2,6,6,-tetramethylpiperidine and the like;polymerizable unsaturated compounds having carbonyl group such asacrolein, diacetonacrylamide, diacetonemethacrylamide, acetoacetoxyethylmethacrylate, formylstyrol, C₄-C₇ vinyl alkyl ketones (e.g., vinylmethyl ketone, vinyl ethyl ketone, vinyl butyl ketone); polyvinylcompounds having at least two polymerizable unsaturated groups permolecule such as allyl (meth)acrylate, ethylene glycol di(meth)acrylate,triethylene glycol di(meth)acrylate, tetraethylene glycoldi(meth)acrylate, 1,3-butylene glycol di(meth)acrylate,trimethylolpropane tri(meth)acrylate, 1,4-butanediol di(meth)acrylate,neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,pentaerythritol di(meth)acrylate, pentaerythritol tetra(meth)acrylate,glycerol di(meth)acrylate, 1,1,1,-trishydroxymethylethanedi(meth)acrylate, 1,1,1-trishydroxymethylethane tri(meth)acrylate,1,1,1-trishydroxymethylpropane tri(meth)acrylate, triallylisocyanurate,diallylterephthalate, divinylbenzene and the like; can be named. Thesecan be used either singly or in combination of two or more, depending onthe performance desired for individual aqueous resin dispersions.

Use ratio of above monomer (A) and monomer (B) is subject to noparticular limitation but may be suitably selected according to theperformance desired of, or the utility intended for, individual aqueousresin dispersions. In general terms, based on the combined amount of themonomer (A) and monomer (B), monomer (A) may be within a range of 1-90wt %, preferably 5-60 wt %, inter alia, 10-40 wt %; and monomer (B),within a range of 10-99 wt %, preferably 40-95 wt %, inter alia, 60-90wt %. Where the use ratio of the monomer (A) is less than 1 wt %,oxidative hardening of the coating film formed with use of the resultingaqueous resin dispersion fails to progress satisfactorily, and alsothick appearance of the coating film is apt to be impaired. On the otherhand, where it exceeds 90 wt %, the hardened coating film formed withuse of the resulting aqueous resin dispersion becomes brittle and thefilm may have insufficient weatherability.

It is preferred to select as the other polymerizable unsaturated monomer(B), so that the theoretical glass transition temperature of the(co)polymer of all of the used monomer(s) (B) should lie within a rangeof 0-100° C., preferably 10-80° C., inter alia, 40-70° C.

The glass transition temperature (absolute temperature) as referred toin this invention is calculated according to the following equation.1/Tg=W ₁ /T ₁ +W ₂ /T ₂ + . . . W _(n) /T _(n)

-   -   in which W₁, W₂ . . . W_(n) are wt % of each monomer [=(used        amount of each monomer/total weight of the monomers)×100]; and        T₁, T₂ . . . . T_(n) are glass transition temperature (absolute        temperature) of each homopolymer of respective monomer. Glass        transition temperatures of the homopolymers of respective        monomers are those values given in “Polymer Handbook” (Second        Edition, ed. by J. Brandrup. E. H. Immergut). Where glass        transition temperature relating to a certain monomer is not        found in the Handbook, a homopolymer having a weight average        molecular weight of around 50,000 of the particular monomer is        synthesized, and the polymer's glass transition temperature is        measured by means of differential scanning thermal analysis.

Where the theoretical glass transition temperature of (co)polymer of thetotal monomer (B) falls within the above-specified range, bothsatisfactory film-forming ability of the resulting aqueous resindispersion and such physical properties of the coating film formed withuse of the aqueous resin dispersion as weatherability, water resistanceand the like can be obtained.

Furthermore, the other polymerizable unsaturated monomer (B) preferablycontains carboxyl-containing polymerizable unsaturated monomer (b1)within a range of 0.1-5 wt %, preferably at least 0.5 wt % but less than3 wt %, based on the total weight of the monomers (A) and (B).

As the carboxyl-containing polymerizable unsaturated monomer (b1), forexample, (meth)acrylic acid, maleic acid, crotonic acid, β-carboxyethylacrylate and the like can be named. Of these, particularly acrylic acid,methacrylic acid and crotonic acid are preferred. By the use of suchcarboxyl-containing polymerizable unsaturated monomer (b1) as at least apart of the other polymerizable unsaturated monomer (B), stability ofresin particles dispersed in the aqueous medium of the resulting aqueousresin dispersion or mechanical stability can be secured. Furthermore,when the aqueous resin dispersion containing such a monomer (b1) isapplied to enamel paint, color matching ability of the paint can beimproved.

The other polymerizable unsaturated monomer (B) preferably comprises,furthermore, as at least a part thereof, 30-90 wt %, preferably 35-85 wt%, inter alia, 45-80 wt %, based on the combined weight of the monomer(A) and monomer (B), of polymerizable unsaturated monomer (b2). Themonomer (b2) contains at least C₄ straight chain, branched chain orcyclic, saturated or unsaturated hydrocarbon group.

As such polymerizable unsaturated monomer (b2) containng at least C₄hydrocarbon group, for example, alkyl or cycloalkyl (meth)acrylates suchas n-butyl (meth)acrylate, i-butyl (meth)acrylate, tert-butyl(meth)acrylate, n-hexyl (meth)acrylate, octyl (meth)acrylate,2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, tridecyl(meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate,“isostearyl acrylate” (Osaka Organochemical Co.), cyclohexyl(meth)acrylate, methylcyclohexyl (meth)acrylate, t-butylcyclohexyl(meth)acrylate, cyclododecyl (meth)acrylate and the like; polymerizableunsaturated compounds having isobornyl group such as isobornyl(meth)acrylate; polymerizable unsaturated compounds having adamantylgroup such as adamantyl (meth)acrylate; and vinyl aromatic compoundssuch as styrene, α-methylstyrene, vinyltoluene and the like can benamed. Use of such polylmerizable unsaturated monomer (b2) having atleast C₄ hydrocarbon group contributes to improve water resistance ofcoating film formed of the particles dispersed in the resulting aqueousresin dispersion.

It is also desirable that the other polymerizable unsaturated monomer(B) comprises, as at least a part thereof, polymerizable unsaturatedmonomer (b3) having at least C₆ straight chain or branched chainhydrocarbon group, in an amount of 1-30 wt %, preferably 5-20 wt %,inter alia, 6-18 wt %, based on the combined weight of the monomers (A)and (B).

As the polymerizable unsaturated monomer (b3) having at least C₆straight or branched chain hydrocarbon group, for example, n-hexyl(meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl(meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, stearyl(meth)acrylate, “isostearyl acrylate” (Osaka Organochemical Co.) and thelike can be named. These can be used either singly or in combination oftwo or more.

Use of such polymerizable unsaturated monomer (b3) containing at leastC₆ straight or branched chain hydrocarbon group as at least a part ofthe other polymerizable unsaturated monomer (B) allows the monomericemulsified product after the concurrent fine granulation of the otherpolymerizable unsaturated monomer (B) with the fatty acid-modifiedpolymerizable unsaturated monomer (A) to maintain polymerizationstability and furthermore enables production of aqueous resindispersions which can form coating film of excellent water resistance.

In the occasion of preparing an aqueous resin dispersion according tothe process of the invention, it is desirable that the otherpolymerizable unsaturated monomer (B) comprises thosecarboxyl-containing polymerizable unsaturated monomer (b1),polymerizable unsaturated monomer (b2) which contains hydrocarbon grouphaving at least 4 carbon atoms and other polymerizable unsaturatedmonomer (b7) other than above fatty acid-modified polymerizableunsaturated monomer (A), monomer (b1) and monomer (b2): that themonomeric mixture (I) to be emulsion polymerized contains, based on thecombined weight of the monomers (A) and (B), 5-50 wt %, preferably 10-40wt %, inter alia, 10-35 wt %, of monomer (A); 0.1-5 wt %, preferably0.5-4.5 wt %, inter alia, 0.5-3 wt %, of monomer (b1); 45-80 wt %,preferably 50-75 wt %, inter alia, 55-70 wt %, of monomer (b2), and0-49.9 wt %, preferably 0-39.5 wt %, inter alia, 0-34.5 wt % of theother polymerizable unsaturated monomer (b7); and the polymerizableunsaturated monomer (b2) containing hydrocarbon group having at least 4carbon atoms comprises, based on the combined weight of the monomers (A)and (B), 1-30 wt %, preferably 5-20 wt %, inter alia, 6-18 wt % of thepolymerizable unsaturated monomer (b3) containing straight or branchedchain hydrocarbon group having at least 6 carbon atoms.

In the above composition, where the use ratio of monomer (A) is lessthan 5 wt %, thick appearance of coating film formed with use ofresulting aqueous resin dispersion becomes insufficient. On thecontrary, where it exceeds 50 wt %, coating film formed from thecomposition may exhibit insufficient weatherability. Where the use ratioof monomer (b1) is less than 0.1 wt %, particles in the resultingaqueous resin dispersion may show insufficient stability. On thecontrary, where it exceeds 5 wt %, coating film formed from theresulting dispersion may have reduced water resistance. Furthermore,where the use ratio of monomer (b2) is less than 45 wt %, coating filmformed from the resulting dispersion may have reduced water resistance.On the other hand, where it exceeds 80 wt %, storage stability ofresulting aqueous resin dispersion may be impaired.

Aqueous resin dispersions can be stably prepared throughcopolymerization of fatty acid-modified polymerizable unsaturatedmonomer (A) and the other polymerizable unsaturated monomer (B) at theabove-specified ratios, and the aqueous resin dispersions can formcoating films having transparency and thick appearance and exhibitingexcellent performance such as water resistance and the like.

It is also desirable that the other polymerizable unsaturated monomer(B) contains, as at least a part thereof, cycloalkyl-containingpolymerizable unsaturated monomer (b4).

As the cycloalkyl-containing polymerizable unsaturated monomer (b4),those compounds having one cycloalkyl group containing at least 6 carbonatoms and one polymerizable unsaturated bond per molecule are suitable.Examples of such compounds include cyclohexyl (meth)acrylate,methylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate,cyclododecyl (meth)acrylate and the like, which can be used eithersingly or in combination of two or more. Of these, cyclohexyl(meth)acrylate is preferred.

Use of cycloalkyl-containing polymerizable unsaturated monomer (b4) asat least a part of the other polymerizable unsaturated monomer (B) canimprove weatherability of coating film formed from the resulting aqueousresin dispersion, and also can improve its water resistance, soilresistance and the like. Where improvement in weatherability isintended, adequate (b4) content is 1-70 wt %, preferably 10-60 wt %,inter alia, 25-45 wt %, based on the combined weight of monomers (A) and(B).

It is also desirable that the other polymerizable unsaturated monomer(B) contains, as at least a part thereof, aromatic vinyl monomer (b5).As the aromatic vinyl monomer (b5), for example, vinyl aromaticcompounds such as styrene, α-methylstyrene, vinyltoluene and the likecan be named, which can be used either singly or in combination of twoor more. Use of such aromatic vinyl monomer (b5) can increasecopolymerizability of total monomers and also can improve physicalproperties of formed coating film, such as water resistance.

In general terms, it is adequate to use such aromatic vinyl monomer (b5)within a range of 150 wt %, preferably 5-45 wt %, inter alia, 12-35 wt%, based on the combined weight of monomers (A) and (B).

In the occasion of preparing an aqueous resin dispersion according tothe process of the invention, it is desirable that the otherpolymerizable unsaturated monomer (B) comprises thosecycloalkyl-containing polymerizable unsaturated monomer (b4), aromaticvinyl monomer (b5), and other polymerizable unsaturated monomer (b8)other than above monomer (A), monomer (b4) and monomer (b5): and thatthe monomeric mixture (I) to be emulsion polymerized contains, based onthe combined weight of the monomers (A) and (B), 5-50 wt %, preferably10-40 wt %, inter alia, 10-35 wt %, of monomer (A); 1-70 wt %,preferably 10-60 wt %, inter alia, 26-45 wt %, of monomer (b4); 1-50 wt%, preferably 5-45 wt %, inter alia, 12-35 wt %, of monomer (b5), and0-93 wt %, preferably 0-75 wt %, inter alia, 0-47 wt % of the otherpolymerizable unsaturated monomer (b8).

In the above composition, where the use ratio of monomer (A) is lessthan 5 wt %, thick appearance of coating film formed with use ofresulting aqueous resin dispersion becomes insufficient. On thecontrary, where it exceeds 50 wt %, coating film formed from thecomposition may exhibit insufficient weatherability. Where the use ratioof monomer (b4) is less than 1 wt %, formed coating film hasinsufficient weatherability. On the contrary, when it exceeds 70 wt %,polymerization stability is occasionally impaired. Furthermore, when useratio of monomer (b5) is less than 1 wt %, water resistance of coatingfilm formed therefrom may be reduced. On the other hand, when it exceeds50 wt %, weatherability of formed coating film may become insufficient.

Through copolymerization of fatty acid-modified polymerizableunsaturated monomer (A) and the other polymerizable unsaturated monomer(B) at the above-specified ratios, aqueous resin dispersions which formcoating films having transparency, thick appearance and particularlyfavorable water resistance and weatherability can be prepared.

Again, in the occasion of preparing an aqueous resin dispersion of thepresent invention, it is desirable that the other polymerizableunsaturated monomer (B) comprises, as at least a part thereof,carbonyl-containing polymerizable unsaturated monomer (b6).

The carbonyl-containing polymerizable unsaturated monomer (b6) includescompounds having one carbonyl group and one polymerizable unsaturatedbond per molecule. More specifically, for example, acrolein, diacetoneacrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate,formyl styrol, C₄-C₇ vinyl alkyl ketone (e.g., vinyl methyl ketone,vinyl ethyl ketone, vinyl butyl ketone) and the like can be named. Thesecan be used either singly or in combination of two or more. Inparticular, diacetone (meth)acrylamide are preferred.

When such carbonyl-containing polymerizable unsaturated monomer (b6) isused as at least a part of the other polymerizable unsaturated monomer(B), and when a later-specified hydrazine derivative is blended with theresulting aqueous resin dispersion, auxiliary crosslinkage of themonomer (b6)-derived carbonyl groups and the hydrazine derivative can bepromoted in addition to the oxidative hardening caused by the fatty acid(a1) component, and drying property of the coating film formed from thedispersion can be further improved. Using this dispersion, paintcompositions capable of forming coating film showing favorable physicalproperties such as weatherability, water resistance and the like can beprepared.

In general terms, such carbonyl-containing monomer (b6) is suitably usedwithin a range of 0.5-35 wt %, preferably 2-20 wt %, based on thecombined weight of the monomers (A) and (B).

Where the other polymerizable unsaturated monomer (B) comprises suchcarbonyl-containing polymerizable unsaturated monomer (b6), kind of thefatty acid (a1) is not particularly limited, which may be semi-dryingoil fatty acid and/or non-drying oil fatty acid. Semi-drying oil fattyacid and/or non-drying oil fatty acid are generally those of lowoxidative hardenability, and those earlier exemplified can be used.

Use ratios of semi-drying oil fatty acid and/or non-drying oil fattyacid and carbonyl-containing polymerizable unsaturated monomer (b6) canbe generally within the following ranges based on the combined weight ofthe monomers (A) and (B): semi-drying oil fatty acid and/or non-dryingoil fatty acid, 5-50 wt %, preferably 10-40 wt %; andcarbonyl-containing polymerizable unsaturated monomer (b6), 0.5-35 wt %,preferably 2-20 wt %. Where semi-drying oil fatty acid and/or non-dryingoil fatty acid component is less than 5 wt %, thick appearance of thecoating film formed from the resulting aqueous resin dispersion may beimpaired. On the contrary, when it exceeds 50 wt %, water resistance ofthe formed coating film may become insufficient. Again, wherecarbonyl-containing polymerizable unsaturated monomer (b6) is less than0.5 wt %, formed coating film has insufficient water resistance andweatherability. On the other hand, when it exceeds 35 wt %, formedcoating film may become brittle.

Use of carbonyl-containing polymerizable unsaturated monomer (b6) as atleast a part of the monomer (B) allows crosslinkage between the carbonylgroups and later-described hydrazine derivative to progress where such ahydrazine derivative is concurrently used. Hence, even when semi-dryingoil fatty acid and/or non-drying oil fatty acid are used as the fattyacid (a1) component, aqueous resin dispersion capable of forming coatingfilm of thick appearance which exhibits favorable weatherability, waterresistance and the like and showing good compatibility with ironsubstrate material can be prepared.

The other polymerizable unsaturated monomer (B) furthermore can comprisehydroxyl-containing (meth)acrylate, for securing stability of finelygranulated monomeric emulsified product at the polymerization stage orstability of particles in aqueous resin dispersions during storage. Asthe hydroxyl-containing (meth)acrylate, those earlier exemplified can beused, and its use ratio is within a range of 1-50 wt %, preferably 1-30wt %, inter alia, 1-10 wt %, based on the combined amount of themonomers A and B.

According to the invention, the monomeric mixture (I) comprises, as theessential components, heretofore described fatty acid-modifiedpolymerizable unsaturated monomer (A) and other polymerizableunsaturated monomer (B) which is copolymerizable with the monomer (A).The monomeric mixture (I) may further contain a compound or compoundswhich do not substantially contain polymerizable unsaturated group.

Use of such monomeric mixture (I) comprising compound(s) which do notsubstantially contain polymerizable unsaturated group allows preparationof particles enclosing said compound(s) as dispersed in the aqueousresin dispersions.

As the compounds which do not substantially contain polymerizableunsaturated group, for example, paint additives such as ultravioletabsorber, ultraviolet stabilizer, metallic dryer and the like; resinssuch as acrylic resin, polyester resin, polyurethane resin, alkyd resinand the like; and coloring agents such as pigment, dye and the like canbe named. These can be used either singly or in combination of two ormore. In particular, at least one selected from the ultravioletabsorber, ultraviolet stabilizer and metallic dryer is preferred.

As the ultraviolet absorber, for example, salicylic acid derivativessuch as phenyl salicylate, p-octylphenyl salicylate, 4-t-butylphenylsalicylate and the like; benzophenone compounds such as2,4-dihyroxybenzophenone, 2-hydroxy-4-methoxybenzophenone,2,2′-dihydroxy-4-methoxybenzophenone,2-hydroxy-4-methoxy-2′-carboxybenzophenone,2-hydroxy-4-methoxy-5-sulfobenzophenone trihydrate,2,2′-dihydroxy-4,4′-dimethoxybenzophenone,2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-octadecyloxybenzophenone,sodium 2-2′-dihydroxy-4,4′-dimethoxy-5-sulfobenzophenone, 2,2′,4,4′-tetrahydroxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone,5-chloro-2-hydroxybenzophenone, resorcinol monobenzoate,2,4-dibenzoylresorcinol, 4,6-dibenzoylresorcinol,hydroxydodecylbenzophenone,2,2′-dihydroxy-4(3-methacryloxy-2-hydroxypropoxy)benzophenone and thelike; benzotriazole compounds such as2-(2′-hydroxy-5′-methylphenyl)-benzotriazole and the like; othercompounds such as oxalic acid anilide, cyanoacrylate and the like; andacrylic copolymers containing above-exemplified ultraviolet absorbingmonomer as a copolymerized component can be named.

As the ultraviolet stabilizer, for example,2-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole,2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole,poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazin-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}],dimethyl succinate1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidinepolycondensate, 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate,bis-(2,2′,6,6′-tetramethyl-4-piperidinyl) cebacate,4-benzoyloxy-2,2′,6,6′-tetramethylpiperidine, acrylic copolymerscontaining above-exemplified ultraviolet-stable monomer as acopolymerized component can be named.

Above ultraviolet absorber and/or ultraviolet stabilizer may be usedsingly or as suitably selected combinations. Generally suitable useratios of the ultraviolet absorber and/or ultraviolet stabilizer are:based on the combined weight of the monomers (A) and (B), ultravioletabsorber, within a range of 0.1-5.0 wt %, in particular, 0.2-0.7 wt %;and the ultraviolet stabilizer, 0.1-5.0 wt %, in particular, 0.2-3.0 wt%.

In the present invention, where the monomeric mixture (I) contains suchultraviolet absorber and/or ultraviolet stabilizer, at least a part ofthe particles dispersed in the resulting aqueous resin dispersionenclose the ultraviolet absorber and/or ultraviolet stabilizer and inconsequence the absorber and/or stabilizer are uniformly dispersed incoating film formed from the aqueous resin dispersion. Furthermore, theyare not eluted out of the formed film by rain water or the like andexhibit their effect stably over a prolonged period.

As the metallic dryer, for example, salts of at least one metal selectedfrom the group consisting of aluminum, calcium, cerium, cabalt, iron,lithium, magnesium, manganese, zinc and zirconium, with acid can benamed. As the acid, for example, capric acid, caprylic acid, isodecanoicacid, linolenic acid, naphthenic acid, neodecanoic acid, actenic acid,oleic acid, palmitic acid, resin acid, ricinoleic acid, soybean oilfatty acid, stearic acid, tall oil fatty cid and the like can be named.

In the present invention, where such a metallic dryer is contained inthe monomeric mixture (I) prior to the polymerization, oxidativehardenability of coating film formed from the resulting aqueous resindispersion can be improved. This is presumably because the metallicdryer is enclosed in at least a part of the particles dispersed in theaqueous resin dispersion, and when the dryer-enclosing particles areformed into film, the metallic dryer can effectively act on oxidativehardening polymerizable unsaturated groups, within the enclosingparticles. Generally suitable use amount of the metallic dryer is, basedon combined weight of the monomers (A) and (B), within a range of 0.5-10wt %, in particular, 1-7 wt %.

In the occasion of fine granulation of the monomeric mixture (I) in anaqueous medium, an emulsifier may be concurrently used where necessary.As the emulsifier, anionic emulsifier and nonionic emulsifier aresuitable. As the anionic emulsifier, for example, sodium salt orammonium salt of alkylsulfonic acid, alkylbenzenesulfonic acid,alkylphosphoric acid and the like can be named. Also as the nonionicemulsifier, for example, polyoxyethylene oleyl ether, polyoxyethylenestearyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecylether, polyoxyethylene phenyl ether, polyoxyethylene nonylphenyl ether,polyoxyethylene octylphenyl ether, polyoxyethylene monolaurate,polyoxyethylene monostearate, polyoxyethylene monooleate, sorbitanmonolaurate, sorbitan monostearate, sorbitan trioleate, polyoxyethylenesorbitan monolaurate and the like can be named.

It is also permissible to use polyoxyalkylene-containing anionicemulsifier which has an anionic group and a polyoxyalkylene group suchas polyoxyethylene group or polyoxypropylene group per molecule orreactive anionic emulsifier having the anionic group and polymerizableunsaturated group per molecule.

Such an emulsifier can be used within a range of 0.1-15 wt %, preferably0.5-12 wt %, based on the combined amount of total monomers.

The monomeric mixture (I) may also contain a chain transfer agent, forthe purpose of adjusting molecular weight of the resulting aqueous resindispersion. Useful chain transfer agent includes compounds havingmercapto group. As specific examples, laurylmercaptan,t-dodecylmercaptan, octylmercaptan, 2-ethylhexyl thioglycolate,2-methyl-5-tert-butylthiophenol, mercaptoethanol, thioglycerol,mercaptoacetic acid (thioglycolic acid), mercaptopropionate,n-octyl-3-mercaptopropionate and the like can be named. Generallysuitable use amount of the chain transfer agent is, based on thecombined amount of total monomers, within the range of 0.05-10 wt %, inparticular, 0.1-5 wt %.

Where necessary, the monomeric mixture (I) may further be blended withorganic solvent such as long chain saturated hydrocarbon solvent likehexadecane, long chain alcoholic solvent like hexadecanol and the like.

According to the present invention, so far described monomeric mixture(I) can form a monomeric emulsified product when it is finely dispersedin an aqueous medium.

Concentration of the monomeric mixture (I) in an aqueous mediumgenerally suitably lies within a range of 10-70 wt %, preferably 20-60wt %, from the standpoint of fine granulation-forming ability of themonomeric emulsified product formed, stability at the polymerizationstage and practical utility when it is applied to water-based paint.

Fine dispersing of the monomeric mixture (I) in an aqueous medium can benormally conducted with a dispersing machine having high-energy shearingability. As useful dispersing machines in that occasion, for example,high-pressure emulsifier, ultrasonic emulsifier, high-pressure colloidmill, high-pressure homogenizer and the like can be named. Thesedispersing machines are normally operable under high pressure levels of10-1000 MPa, preferably around 50-300 MPa. The monomeric mixture may bepreliminarily emulsified with a dispersing device or the like, inadvance of the machine dispersing.

Suitable average particle diameter of the particles dispersed in themonomeric emulsified product, which is obtained upon finely dispersingthe monomeric mixture (I) with above-described means, is not more than500 nm, preferably within the range of 80-400 nm, inter alia, 100-300nm, in consideration of transparency and water resistance of formedcoating film.

Polymerization of thus obtained monomeric emulsified product can beconducted, for example, through the steps of feeding the entire amountof the monomeric emulsified product after the fine dispersion into areactor equipped with a stirrer, adding a polymerization initiator andheating the system under stirring, following known mini-emulsionpolymerization method.

As the polymerization initiator, either oil-soluble or water-solubletype can be used. As examples of oil-soluble polymerization initiator,organic peroxides such as benzoyl peroxide, octanoyl peroxide, lauroylperoxide, stearoyl peroxide and the like; and azo compounds such asazobisisobutyronitrile, azobis(2,4-dimethylvaleronitrile) and the likecan be named. As examples of water-soluble initiator, organic peroxidessuch as cumene hydroperoxide, tert-butyl peroxide, tert-butylperoxylaurate, tert-butyl peroxyisopropylcarbonate, tert-butylperoxyacetate, diisopropylbenzene hydroperoxide and the like; azocompounds such as azobis(2-methylpropionitrile),azobis(2-methylbutyronitrile), 4,4′-azobis(4-cyanobutanoic acid),dimethylazobis-(2-methylpropionate),azobis[2-methyl-N-(2-hydroxyethyl)-propionamide],azobis{2-methyl-N-[2-(1-hydroxybutyl)]-propionamide} and the like; andpersulfates such as potassium persulfate, ammonium persulfate, sodiumpersulfate and the like can be named. These may be used either singly orin combination of two or more. Where necessary, a reducing agent such assugar, sodiumformaldehyde sulfoxylate, iron complex or the like may beused concurrently with such polymerization initiator to form a redoxpolymerization system.

Preferred use amount of the polymerization initiator ranges 0.1-5 wt %,in particular, 0.2-3 wt %, based on the combined weight of the monomers(A) and (B). Means to add the polymerization initiatior is subject to noparticular limitation and can be suitably selected depending on its kindor amount. For example, it may be contained in the monomeric mixture (I)or in the aqueous medium in advance, or added at one time or dropwiseduring polymerization.

According to the invention, where the aqueous resin dispersion containsacidic groups, it is desirable to neutralize them with a neutralizingagent, for improving mechanical stability of particles dispersed in theaqueous resin dispersion. The neutralizing agent is subject to nolimitation so long as it can neutralize acidic groups. For example,sodilum hydroxide, potassium hydroxide, trimethylamine,dimethylaminoethanol, 2-methyl-2-amino-1-propanol, triethylamine,aqueous ammonia and the like can be named. These neutralizing agents aredesirably used in such respective amount as will render pH of theaqueous resin dispersion after the neutralization about 6.5-9.0.

According to the so far described process of the present invention, anaqueous resin dispersion in which the dispersed resin has an averageparticle diameter not greater than 500 nm, in particular, within therange of 100-300 nm can be prepared. The average particle diameter ofthe dispersed resin in each aqueous resin dispersion depends on theaverage particle diameter of dispersed particles in the monomericemulsified product prior to polymerization. Where the average diameterof the particles dispersed in the monomeric emulsified product prior tothe polymerization is caused to lie within the above-specified range,variation ratio of average particle diameter of dispersed resin in theaqueous resin dispersion to that of the dispersed particles in themonomeric emulsified product can be generally kept within a range of50-150%, in particular, at least 60% but less than 100%, inter alia,70-99%. Said variation ratio can be caluculated according to thefollowing equation: $\begin{matrix}{{variation}\quad{ratio}\quad{in}\quad{average}} \\{{particle}\quad{{diameter}(\%)}}\end{matrix} = {\frac{\begin{matrix}{{{average}\quad{particle}}\quad} \\{{diameter}\quad({nm}){of}\quad{resin}} \\{{{dispersed}\quad{in}\quad{aqueous}}\quad} \\{{resin}\quad{dispersion}}\end{matrix}}{\begin{matrix}\begin{matrix}{{average}\quad{particle}\quad{diameter}} \\{({nm}){of}\quad{particles}\quad{dispersed}}\end{matrix} \\{{in}\quad{monomeric}} \\{{emulsified}\quad{product}}\end{matrix}} \times 100.}$

Where the variation ratio of average particle diameter lies within theabove-specified range, the emulsion polymerization can be stablyconducted, and the average particle diameter of the resin dispersed inthe eventually obtained aqueous resin dispersion can be made to fallwithin the above-specified range (not greater than 500 nm, inparticular, 80-400 nm, inter alia, 100-300 nm) to enable formation oftransparent hardened coating film.

It is generally desirable for aqueous resin dispersions which areprepared according to the process of the invention to haveweight-average molecular weight ranging 10,000-300,000, in particular,30,000-200,000. Weight-average molecular weight as referred to in thepresent specification is the value obtained by converting weight-averagemolecular weight of a sample dispersion using tetrahydrofuran as thesolvent, as measured by means of gel permeation chromatography, based onweight-average molecular weight of polystyrene. As the column used inthe gel permeation chromatography, “TSKgel G-4000H×L”, “TSKgelG-3000H×L”, “TSKgel G-2500H×L” and “TSKgel G-2000H×L” (tradenames,products by Tosoh Corporation) can be named.

It is generally convenient for the aqueous resin dispersions to have anoil length within a range of 0.5-45%, preferably 3-30%, inter alia,10-25%. Where the oil length is less than 0.5%, coating film formedtherefrom exhibits insufficient oxidative hardenability. On the otherhand, where it exceeds 45%, the coating film tends to become hard andbrittle as its drying time passes and may come to have inferiorperformance in weatherability, alkali resistance and the like. In thepresent specification, oil length refers to weight percentile value offatty acid contained in solid component of an aqueous resin dispersion.

Aqueous Resin Compositions

Aqueous resin compositions provided by the invention comprise thoseaqueous resin dispersions obtained as above-described.

The aqueous resin compositions may additionally contain hydrazinederivatives.

As specific examples of the hydrazine derivatives, C₂-C₁₈ saturateddicarboxylic acid dihydrazides such as oxalic acid dihydrazide, malonicacid dihydrazide, glutaric acid dihydrazide, succinic acid dihyrazide,adipic acid dihydrazide, sebacic acid dihydrazide and the like;monoolefinic unsaturated dicarboxylic acid dihydrazides such as maleicacid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazideand the like; terephtalic acid dihydrazide or isophthalic aciddihydrazide; pyromellitic acid dihydrazide, trihydrazide ortetrahydrazide; nitrilotrihydrazide, citric acid trihydrazide,1,2,4-benzene trihydrazide, ethylenediaminetetraacetic acidtetrahydrazide, 1,4,5,8-naphthoic acid tetrahydrazide; polyhydrazidesobtained through reaction of low molecular weight polymers havingcarboxylic acid lower alkyl ester groups with hydrazine or hydrazinehydrate; hydrazide-containing compounds such as carbonic aciddihydrazide and the like; bis-semicarbazide; polyfunctionalsemicarbazides which are obtained by reacting diisocyanate such ashexamethylene diisocyanate, isophorone diisocyanate, or polyisocyanatecompounds derived therefrom with excessive N,N-substituted hydrazinessuch as N,N-dimethylhydrazine or above-exemplified hydrazides, aqueouspolyfunctional semicarbazides which are obtained by reacting isocyanategroups in reaction products of above polyisocyanate compounds withpolyether and active hydrogen compounds containing hydrophilic groups,such as polyols or polyethylene glycol monoalkyl ethers, with excessiveamount of above-exemplified dihydrazide; compounds having semicarbazidegroups such as mixtures of the polyfunctional semicarbazide and aqueouspolyfunctional semicarbazide; and compounds having hydrazone groups suchas bis-acetyl dihydrazone and the like can be named.

Where the aqueous resin compositions contain such hydrazine derivatives,coating film formed therefrom absorbs harmful substances in the air, forexample, formaldehyde, and are useful for removal of these harmfulsubstances. Furthermore, where the aqueous resin dispersion has carbonylgroups, such a hydrazine derivative can act as a crosslinking agent forauxiliary crosslinkage.

Desirable amount of the hydrazine derivative to be blended lies, basedon the solid resin content of the aqueous resin dispersion, generallywithin a range of 0.01-10 wt %, in particular, 0.1-8 wt %.

The aqueous resin compositions may further contain, where necessary,such additives as wetting agent, defoaming agent, plasticizer,film-forming assistant, organic solvent, thickener, antiseptic,antifungus agent, pH regulating agent, hardening catalyst, surfacetreating agent and the like, in suitable selective combination. Thosealready explained metallic dryer, ultraviolet absorber and ultravioletstabilizer may also be contained in the aqueous resin compositions.

The aqueous resin compositions provided by the present invention arehardenable even at ambient temperatures, and resulting hardened filmsare transparent. More specifically, transmission haze value of thehardened films, for example, can be made 5 or less. This transmissionhaze value is determined as follows. On a transparent sheet whosetransmission haze value has been measured with “COH-300A” (acolor-difference. turbidity measuring machine, Nihon Denshoku KogyoCo.), a test sample is applied to a dry film thickness of 20 μm and agedfor a week at 20° C. to provide a test specimen. Transmission haze valueof this test specimen is measured with COH-300A, and the transmissionhaze value of the transparent sheet is subtracted from the measuredvalue.

Thus the aqueous resin compositions can be put to various uses such aspaints for architecture, outer panels of automobiles, car parts and thelike, coating materials like printing ink, paint additives, joiningagent for non-woven fabric, adhesives, fillers, molding materials,resist and the like.

Water-Based Paint Compositions

This invention also provides water-based paint compositions whichcontain above aqueous resin compositions.

The water based paint compositions can be used as clear paint or enamelpaint.

Where they are used as enamel paint, coloring pigment, effect pigment,extender, rust preventive pigment or the like which are known in the artof paint can be blended as pigment component.

For example, it is generally desirable for the water-based paintcompositions containing titanium white, to contain titanium white at apigment volumetric concentration (PVC) within a range of 5-25%,preferably 7-22%, for retaining thick appearance of formed coating filmand having glossy finish. As the titanium white, rutile type ispreferred from the standpoint of weatherability. Here the “pigmentvolumetric concentration” refers to the volumetric ratio of blendedpigment component to the combined solid content of total resin componentand total pigment in the concerned paint. In the present specification,specific gravity value of each pigment which provides the basis forcalculating the pigment's volume conforms to “Toryo Genryo Binran”(manual of paint materials), 6th ed. (Nihon Paint Industries CorporationAssociation) and specific gravity of solid resin content is assumed tobe approximate to 1.

The water-based paint compositions may contain, other than theabove-described components, modifying resins such as water-soluble oremulsifiable acrylic resin, alkyd resin, silicone resin,fluorine-containing resin, epoxy resin, urethane resin, polyester resinand the like; pigment-dispersing agent, surfactant, dispersant,defoaming agent, thickener, film-forming assistant, antiseptic,antifungus agent, anti-freezing agent, pH regulator, flash rustinhibitor, aldehyde capturing agent, laminar clay mineral, powdery orfine particulate active carbon, titanium oxide as an optical catalyst,antifouling agent such as polyalkylene glycol-modified alkyl silicateand the like. These additives can be contained either singly or incombination of two or more.

The water-based paint compositions can be applied onto new substratesurfaces or old coating film-applied surfaces. Materials constitutingthe substrate are subject to no particular limitation, which may be, forexample, inorganic substrate such as concrete, mortal, slate plate, PCplate, ALC plate, cement calcium silicate plate, concrete blocks, wood,stone and the like; organic substrate such as plastics; and metals suchas iron, aluminum and the like. As old coating films, those of acrylicresin, acrylic-urethane resin, polyurethane resin, fluorine-containingresin, silicone-acrylic resin, vinyl acetate resin, epoxy resin, alkydresin and the like, which have been applied onto those substrates, canbe named. These old coated surfaces may be applied with water-based orsolvent-based undercoat, and where necessary, a water-based paintcomposition of the present invention can be applied onto theundercoat-applied surface. It is also possible to apply a water-basedpaint composition of the invention as an undercoat and thereafter applya known water-based top coat thereonto.

Because the fatty acid component of the aqueous resin dispersion in thewater-based paint compositions of the present invention is highlycompatible with iron, the compositions are suitable to provideprotective film on iron substrate or coated iron substrate surface.Single or plural applications of the composition are sufficient tomaintain appearance for a long term.

In applying a water-based paint composition of the present inventiononto metallic surface of iron substrate or the like, the compositiondesirably contains 1-10%, in particular, 2-8% of phosphoric acid-derivedpigment, in terms of PVC.

It is desirable that the phosphoric acid-derived pigments are thosewhich are readily dispersible in the presence of high molecularsurfactant, from the viewpoint of corrosion resistance and gloss. Asspecific examples of such phosphoric acid-derived pigment, zincphosphate, zinc phosphosilicate, zinc aluminum phosphate, zinc calciumphosphate, calcium phosphate, aluminum pyrophosphate, calciumpyrophosphate, aluminum dihydrogentripolyphosphate, aluminiummetaphosphate, calcium metaphosphate, zinc phosphomolybdate, aluminumphosphomolybdate and the like can be named.

The water-based paint compositions of the invention may also contain atleast one basic compound selected from the group consisting of nitrousacid salt, phytic acid salt, tannic acid salt and polyamine compounds.As nitrous acid salt, for example, sodium nitrite, calcium nitrite,strontium nitrite, barium nitrite, ammonium nitrite and the like can benamed. As phytic acid salt, for example, sodium phytate, potassiumphytate and the like can be named. As tannic acid salt, for example,sodium tannate, potassium tannate and the like can be named, and aspolyamine compound, for example, N-(2-hydroxyethyl)-ethylenediaminetriacetate (HEDTA), ethylenediamine tetraacetate (EDTA),diethylenetriamine pentaacetate (DTPA), propylenediamine tetraacetate(PDTA), iminodiacetic acid, nitrilotriacetic acid (NTA),diethylenetriaminepentamethylenephosphoric acid (DTPMP), and theiralkali metal salts, and intercalational compound formed by intercalatingmonoalkylamine or polyamine, quaternary ammonium ion and the like intolaminar phosphate such as aluminum dihydrogentripolyphosphate, and thelike can be named. These can be used either singly or in combination oftwo or more.

Addition of these basic compounds enables to prevent occurrence of rustspots in coating film formed by directly applying a water-based paintcomposition onto a metallic surface, as rust on the metallic surfacebleeds onto the coated surface. Suitable amount of the basic compound tobe added lies within a range of 0.02-2 wt %, in particular, 0.05-1 wt %,based on the weight of the concerned water-based paint composition.

Water-based paint compositions of the present invention can be appliedby such means as air spray, airless spray, electrostatic application,brushing, roller coating, texture gun, universal gun and the like.Drying can be effected by any of heat drying, forced drying and ambienttemperature drying. In the present specification, drying condition atlower than 40° C. is referred to as ambient temperature drying, dryingcondition at no lower than 40° C. but lower than 80° C. is referred toas forced drying, and drying condition at 80° C. or above, as heatdrying. Application rate of a water-based paint composition of thepresent invention can be, for example, within a range of 50-300 g/m².

EXAMPLES

Hereafter the present invention is more specifically explained referringto working examples, in which parts and % are wt parts and wt %.

Preparation of Fatty Acid-Modified Monomers

Production Example 1

The following components were placed in a reaction vessel and reacted atreaction temperature of 140° C. under stirring, to provide a fattyacid-modified monomer (a-1). The reaction of epoxy groups with carboxylgroups was monitored by measuring the amount of residual carboxylgroups. About 5 hours were required for completing the reaction.Safflower oil fatty acid 280 parts Glycidyl methacrylate 142 parts.

Production Example 2

Production Example 1 was repeated except that the reacted componentswere changed to the following, to provide a fatty acid-modified monomer(a-2). Linseed oil fatty acid 280 parts Glycidyl methacrylate 142 parts.

Production Example 3

Production Example 1 was repeated except that the reacted componentswere changed to the following, to provide a fatty acid-modified monomer(a-3). Coconut oil fatty acid 210 parts Glycidyl methacrylate 142 parts.

Production Example 4

The following components were put in a reaction vessel and heated to120° C. under stirring. Safflower oil fatty acid 2240 parts Hydroquinone  1.8 parts Methylsulfuric acid   2.6 parts Toluene  144 parts.

Then a mixture of the following components was dropped into the reactionvessel over a period of 2 hours. Hydroxyethyl methacrylate 1300 partsHydroquinone   2.6 parts Methylsulfuric acid   5.6 parts Toluene  234parts.

After the dropping ended, the temperature was raised to 150° C., and thereaction was continued for about 5 hours until the acid value waslowered to not higher than 8.7. Thereafter the toluene was removed underreduced pressure until the heating residue reached at least 95%, toprovide a fatty acid-modified monomer (a-4).

Preparation of Aqueous Resin Dispersions

The following components were put in a glass beaker and stirred with adispersing device at 2,000 rpm for 15 minutes to provide a pre-emulsion.This pre-emulsion was high-pressure treated at 100 MPa with ahigh-pressure emulsifying apparatus in which the fluid was mutuallycollided with exertion of high pressure energy, to provide a monomericemulsified product in which the average diameter of the dispersedparticles was 190 nm. Composition of the monomeric emulsified productFatty acid-modified monomer (a-1) 30 parts n-Butyl methacrylate 25 partsi-Butyl methacrylate 27 parts 2-Ethylhexyl methacrylate 17 partsMethacrylic acid  1 part “Newcol707 SF” (note 1) 10 parts Deionizedwater 85 parts

Then the monomeric emulsified product was transferred into a flask anddiluted with deionized water to a solid concentration of 45%. Afterraising its temperature to 85° C., an aqueous initiator solution of 2 gof VA-086 (note 2) as dissolved in 64.7 g of deionized water was throwninto the flask, followed by 3 hours' stirring during which the sametemperature was maintained. Thereafter an aqueous initiator solution of0.5 g of VA-086 (note 2) as dissolved in 16.2 g of deionized water wasadded to the flask. While the same temperature was maintained, thecontent in the flask was stirred for an hour, cooled to 40° C., and itspH was adjusted to 8.0 with dimethylaminoethanol, to provide an aqueousresin dispersion (I-1) having a solid concentration of 40%, in which thedispersed resin had an average particle diameter of 185 nm.

-   -   (note 1) Newcol707SF: tradename, Nihon Emulsifier Co., an        anionic emulsifier having polyoxyethylene chain; active        component, 30%    -   (note 2) VA-086: tradename, Wako Pure Chemical Industries, Ltd.,        2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide]

Examples 2-14 and Comparative Example 1

In the manner identical with Example 1 except that the blendedcomposition of monomeric emulsified product was changed as shown inTable 1, aqueous resin dispersions (I-2)-(I-14) and (I-15) wereobtained. TABLE 1 Comparative Example Example 1 2 3 4 5 6 7 8 9 10 11 1213 14 1 2 Compo- aqueous resin I-1 I-2 I-3 I-4 I-5 I-6 I-7 I-8 I-9 I-10I-11 I-12 I-13 I-14 I-15 I-16 sition dispersion fatty acid- 30 30 30 3030 30 30 60 30 40 30 30 modified monomer (a-1) fatty acid- 30 30 30modified monomer (a-2) styrene 15 n-butyl methacrylate 25 25 25 25 10 2537 25 i-butyl methacrylate 27 27 27 27 27 27 24 24 24 24 15 25 14 27 37t-butyl methacrylate 25 25 25 22 22 22 22 22 27 2-ehtylhexyl 17 17 17 1717 17 13 13 13 13 20 20 17 25 17 methacrylate methacrylic acid 1 1 1 1 11 1 1 1 1 1 1 1 1 1 diacetone 10 10 10 10 acrylamide n-octyl-3- 0.5 0.50.5 0.5 0.5 mercaptopropionate DICNATE1000W 3.2 3.2 3.2 3.2 3.2 3.2(note 3) Newco1707SF 10 10 10 10 10 10 10 10 10 10 10 13.3 10 10 10 10(note 1) deionized water 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85Property glass transition 25.2 55 25.2 25.2 55 55 58.2 58.2 58.2 58.291.4 21 34.2 25.2 23.9 43.7 values temperature/° C. weight-average 150150 150 80 150 80 150 80 150 80 150 150 150 80 150 150 molecular weightthou. thou. thou. thou. thou. thou. thou. thou. thou. thou. thou. thou.thou. thou. thou. thou. oil length 19.9 19.9 19.9 19.9 19.9 19.9 19.919.9 19.9 19.9 39.8 19.9 26.5 19.9 0 19.9 average particle 190 185 250250 248 240 190 190 245 245 180 190 185 190 180 8100 diameter (nm) ofmonomeric emulsified product average particle 185 183 235 235 232 230179 175 240 240 178 173 175 180 173 150 diameter (nm) of aqueous reindispersion

-   -   (note 3) DICNATE1000W: Tradename: Dainippon Ink & Chemicals,        Inc., metallic dryer, Co content, 3.6%

Comparative Example 2

The monomers, an emulsifier and deionized water were put in a glassbeaker at the blend ratio as indicated in Table 1, and stirred withdispersing device at 2,000 rpm for 15 minutes to provide a monomericemulsified product. Average particle diameter of the particles dispersedin the monomeric emulsified product was 8,100 nm. To this monomericemulsified product 2 g of VA-086 (note 2) was added, followed bystirring until the added polymerization initiator was dissolved.Separately, 0.08 g of Newcol707 SF (note 1) and 50 g of deionized waterwere put in a flask and heated to 85° C. While maintaining saidtemperature inside the flask, the monomeric emulsified product and anaqueous solution of 0.5 g of VA-086 as dissolved in 10 g of deionizedwater were dropped into the flask over 4 hours under stirring. Aftertermination of the dropping, the system was aged for an hour and anaqueous initiator solution of 0.25 g of VA-086 (note 2) as dissolved in3.0 g of deionized water was added into the flask. After further anhour's aging, an aqueous resin dispersion (I-16) was obtained. Thisaqueous resin dispersion left a large quantity of filtration residue.The residue was removed and the filtrate was sampled. In the dilutedsample, the resin dispersed therein had an average particle diameter of150 nm.

Comparative Example 3

Seventy 70 parts of toluene was put in a flask and heated to 100° C. Amonomeric mixture of the following composition as prepared in a separatevessel was dropped into the flask over 4 hours under stirring, whilesaid temperature was maintained. After termination of the dropping thesystem was aged for an hour, and an initiator solution of 5.0 g oft-butylperoxy-2-ethylhexanoate as dissolved in 1.0 g of toluene wasadded dropwise over an hour, followed by another hour's aging.Thereafter the system was cooled to 40° C., to provide a fattyacid-modified acrylic resin. Per 100 g of the fatty acid-modifiedacrylic resin, 5 g of Newcol707 SF was added, stirred, and diluted withdeionized water to the solid content of 33%. The mixture was givenforced stirring to provide an aqueous dispersion, heated, and thetoluene was removed under reduced pressure to provide an autoemulifiableaqueous resin dispersion (I-17). Composition of the monomeric mixtureFatty acid-modified monomer (a-1) 30 parts n-Butyl methacrylate 25 partsi-Butyl methacrylate 27 parts 2-Ethylhexyl methacrylate 15 partsMethacrylic acid  3 parts Toluene 15 parts t-Butylperoxy-2-ethylhexanoate 1.2 parts 

Example 15

The following components were put in a glass beaker and stirred withdispersing device at 2,000 rpm for 15 minutes to provide a pre-emulsion.The pre-emulsion was given a high pressure treatment with ahigh-pressure emulsifying apparatus in which the fluid was mutuallycollided under exertion of high-pressure energy at 100 MPa. Thus amonomeric emulsified product in which the dispersed particles had anaverage particle diameter of 190 nm was obtained. Composition ofmonomeric emulsified product Fatty acid-modified monomer (a-2) 30.15parts Styrene 15 parts Hydroxyethyl methacrylate 4.5 parts i-Butylmethacrylate 20.35 parts t-Butyl methacrylate 20 parts 2-Ethylhexylmethacrylate 8 parts Methacrylic acid 2 parts Newcol707SF (note 1) 10parts Deionized water 85 parts

Then the monomeric emulsified product was transferred to a flask anddiluted with deionized water to the solid content of 45%. Then thetemperature inside the flask was raised to 85° C., an aqueous initiatorsolution of 1.0 part of ammonium persulfate as dissolved in 15 parts ofdeionized water was thrown into the flask, and the content of the flaskwas stirred for 3 hours while said temperature was maintained. Then anaqueous initiator solution of 0.3 part of ammonium persulfate asdissolved in 2.7 parts of deionized water was added to the flask,followed by an hour's stirring while the same temperature wasmaintained. Then the system was cooled to 400 and its pH was adjusted to8.0 with dimethylaminoethanol, to provide an aqueous resin dispersion(I-18) having a solid concentration of 40%. The resin dispersed thereinhad an average particle diameter of 165 nm.

Examples 16-33

Above Example 15 was repeated except that the blended composition waschanged to those as indicated in the following Tables 2 and 3, toprovide aqueous resin dispersions (I-19)-(I-36).

Comparative Example 4

The pre-emulsion as obtained in Example 1 was stirred with a dispersingmachine having high shearing ability, at 10,000 rpm for 5 minutes, toprovide a monomeric emulsified product in which the dispersed particleshad an average particle diameter of 520 nm. Except the above operationsame composition of blended components and procedures as Example 1 wereused to provide an aqueous resin dispersion (I-37) in which thedispersed resin had an average particle diameter of 630 nm. TABLE 2Example 15 16 17 18 19 20 21 22 Composition aqueous resin dispersionI-18 I-19 I-20 I-21 I-22 I-23 I-24 I-25 fatty acid-modified monomer30.15 (a-1) fatty acid-modified monomer 30.15 30.15 30.15 30.15 30.1530.15 30.15 (a-2) styrene 15 15 15 15 15 15 15 15 hydroxyethylmethacrylate 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 i-butyl methacrylate 20.3520.35 20.35 20.35 20.35 17.35 18.35 18.35 t-butyl methacrylate 20 20 2020 20 20 18 18 2-ethylhexyl acrylate 8 8 2-ethylhexyl methacrylate 8 8 88 8 8 methacrylic acid 2 2 2 2 2 2 acrylic acid 2 itaconic acid 2diacetone acrylamide 3 cyclohexyl methacrylate RUVA-93 (note 4) 24-(meth)acryloyloxy-1,2,2,6,6,- 2 pentamethylpiperidine TINUVINE 384-2(note 5) 0.5 TINUVINE 123 (note 6) 0.5 n-octyl-3-mercaptopropionate 0.30.3 0.3 0.3 0.3 0.3 0.3 0.3 cobalt naphthenate 1.5 zirconium octenate 2calcium naphthenate 1 Newco1707SF (note 1) 10 10 10 10 10 10 10 10deionized water 85 85 85 85 85 85 85 85 Property glass transitiontemperature 63 63 70.7 71.5 72.9 73.3 72.4 72.4 values weight-averagemolecular 110 110 110 110 110 110 110 110 weight thou. thou. thou. thou.thou. thou. thou. thou. oil length 20 20 20 20 20 20 20 20 averageparticle diameter 190 185 195 180 193 212 190 190 (nm) of monomericemulsified product average particle diameter 165 160 173 160 165 180 160165 (nm) of aqueous resin dispersion(note 4)RUVA-93; tradename, Otsuka Chemical Co.,2-(2′-hydroxy-5′-methacryloxyethylphenyl-2H-benzotriazole(note 5)TINUVINE 384-2: tradename, Ciba Specialty Chemicals, a benzotriazoleultraviolet absorber(note 6)TINUVINE 123: tradename, Ciba Specialty Chemicals, a piperazineultraviolet stabilizer

TABLE 3 Compar- ative Example Example 23 24 25 26 27 28 29 30 31 32 33 4Compo- aqueous resin I-26 I-27 I-28 I-29 I-30 I-31 I-32 I-33 I-34 I-35I-36 I-37 sition dispersion fatty acid-modified 30 monomer (a-1) fattyacid-modified 30.15 30.15 30.15 30.15 30.15 30.15 monomer (a-2) fattyacid-modified 33.33 33.33 33.33 33.33 monomer (a-3) fatty acid-modified30 monomer (a-4) Styrene 15 15 12 15 15 15 15 15 15 15 hydroxyethyl 4.5methacrylate n-butyl methacrylate 22.85 30 25 25 i-butyl methacrylate10.35 27 27 t-butyl methacrylate 7.85 7.85 27.85 7 24.7 14.7 4.7 19.72-ehtylhexyl 15 15 10 acrylate 2-ehtylhexyl 8 20 10.85 20 20 17 17methacrylate isostearyl acrylate 5 1 methacrylic acid 2 2 2 2 2 2 2 2 22 1 diacetone 3 5 5 5 5 acrylamide cyclohexyl 30 30 30 30 5 30 30 5methacrylate n-octyl-3- 0.3 0.5 0.5 0.5 0.3 0.5 0.3 0.3 0.5 0.3mercaptopropionate cobalt naphthenate 1.5 zirconium octenate 2 calciumnaphthenate 1 Newco1707 10 10 10 10 10 10 10 10 10 10 10 10 SF (note 1)deionized water 85 85 85 85 85 85 85 85 85 85 85 85 Property glasstransition 67.6 64.1 46.8 48.2 66.7 55.7 63.1 61.8 57.7 60.8 25.2 25.2values temperature/° C. weight-average 110 80 80 80 110 80 110 110 80110 150 150 molecular weight thou. thou. thou. thou. thou. thou. thou.thou. thou. thou. thou. thou. oil length 20 20 20 20 20 20 20 20 20 2019.9 19.9 average particle 185 185 190 195 185 205 210 210 220 205 190520 diameter (nm) of monomeric emulsified product average particle 170210 175 180 165 195 185 250 200 185 185 630 diameter (nm) of aqueousresin dispersionPreparation of Aqueous Resin Compositions

Examples 34-66 and Comparative Examples 5-8

Aqueous resin compositions were obtained at the blend ratios asindicated in the following Table 4. Storage stability and transparencyof each of the aqueous resin compositions were evaluated according tothe following standards. The results are concurrently shown in Table 4.TABLE 4 Example 34 35 36 37 38 39 40 41 42 43 44 45 46 Compo- aqueousresin 1-1 I-2 1-3 I-4 I-5 I-6 I-7 I-8 I-9 I-10 I-11 I-12 I-13 sitiondispersion aqueous resin 250 250 253 253 253 253 250 250 253 253 250 250250 dispersion, amount DICNATE 3.2 3.2 3.2 3.2 3.2 3.2 3.2 1000W (note3) adipic acid 0.25 0.25 0.25 0.25 0.25 0.25 3.25 3.25 3.25 3.25 0.250.25 0.25 dihydrazide TEXANOL 15 15 15 15 15 15 15 15 15 15 15 15 15(note 7) Eval- transmission 0.00 0.00 0.09 0.08 0.08 0.07 0.00 0.00 0.090.08 0.05 0.00 0.05 uation haze value storage stability ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯◯ ◯ ◯ ◯Δ ◯ Example 47 48 49 50 51 52 53 54 55 56 57 58 59 Compo- aqueousresin I-14 I-18 I-19 I-20 I-21 I-22 I-23 I-24 I-25 I-26 I-27 I-28 I-29sition dispersion aqueous resin 250 250 250 250 250 253 250 250 250 250250 250 253 dispersion, amount DICNATE 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.23.2 3.2 3.2 1000W (note 3) adipic acid 0.25 0.25 0.25 0.25 0.25 0.253.25 0.25 0.25 0.25 0.25 3.25 0.25 dihydrazide TEXANOL 15 15 15 15 15 1515 15 15 15 15 15 15 (note 7) Eval- transmission 0.00 0.00 0.08 0.090.08 0.10 0.08 0.08 0.03 0.05 0.03 0.05 0.03 uation haze value storagestability ◯ ◯ ◯ ◯ ◯ ◯Δ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Example Comparative example 60 6162 63 64 65 66 5 6 7 8 Compo- aqueous resin I-30 I-31 I-32 I-33 I-34I-35 I-36 I-15 I-16 I-17 I-37 sition dispersion aqueous resin 250 250250 250 250 250 250 250 250 200 250 dispersion, amount DICNATE 3.2 3.23.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 1000W (note 3) adipic acid 0.25 0.255.25 5.25 5.25 5.25 0.25 0.25 0.25 0.25 0.25 dihydrazide TEXANOL 15 1515 15 15 15 15 15 15 15 15 (note 7) Eval- transmission 0.03 0.00 0.080.08 0.09 0.08 0.00 0.00 6.85 1.35 3 uation haze value storage ◯ ◯ ◯ ◯ ◯◯ ◯ ◯ ◯ ◯Δ X stability(note 7)TEXANOL: tradename, Eastman Chemical Co.,2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, film-forming assistant(*1) Transparency

Transparency was evaluated by measuring transmission haze value. Onto anOHP sheet whose transmission haze value had been measured in advancewith COH-300A (tradename, Nippon Denshoku Kogyo, a colordifference-turbidity measuring machine), each aqueous resin compositionwas applied to a dry film thickness of 20 μm, and aged for 20° C. for aweek to provide test specimens. Transmission haze values of these testspecimens were measured with COH-300A (tradename, Nippon Denshoku Kogyo,a color difference-turbidity measuring machine). Subtracting from themeasured values the transmission haze value of the OHP sheet, theremaining values were indicated as transparency of the respective testspecimens. Lower values signify better transparency.

(*2) Storage Stability

One (1) kg of each of the aqueous resin compositions was put inIL-capacity can with coated inner surface, sealed in nitrogen atmosphereand stored for 30 days at 40° C. Thereafter the temperature was droppedto ambient level. Condition of the compositions in the containers wasvisually observed and evaluated according to the following standards.

-   -   ◯: Initial state was retained and no change occurred.    -   ◯Δ: Soft caking or varnish separation was observed but initial        state was restored when stirred.    -   x: Viscosity increased.        Preparation of Water-Based Paint Compositions

Examples 67-100 and Comparative Examples 9-12

Those components as shown under Composition (A) in Table 5 weresuccessively charged in a container each and stirred with a dispersingdevice for 30 minutes to homogeneity to provide pigment pastes. Then theaqueous resin dispersions (I-1)-(I-37) were each added to the pigmentpastes, followed by successive addition of the components as shown underComposition (B) in Table 5, to provide water-based paint compositions.The compositions were then evaluated according to the followingstandards. The results are also shown in Table 5 concurrently with thewater-based paint compositions' property values. TABLE 5 Example 67 6869 70 71 72 73 74 75 Composition city water 40 40 40 40 40 40 40 40 40(A) ethylene glycol 2 2 2 2 2 2 2 2 2 SURAOFF 72N (note 8) 0.8 0.8 0.80.8 0.8 0.8 0.8 0.8 0.8 NOPCOSANT K (note 9) 2 2 2 2 2 2 2 2 2 ADEKANOLUH-438 (note 10) 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 Titanium White102.4 102 102.4 102 102 102 102 102.4 102 JR-600A (note 11) SUNLITESL-1500 (note 12) 10 10 10 10 10 LF BOUSEI P-W-2 (note 13) 13 13 13 SNDefoamer 380 (note 14) 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 aqueous resinI-1 I-1 I-2 I-3 I-4 I-5 I-6 I-7 I-8 dispersion aqueous resin 250 250 250253.2 253.2 253.2 253.2 250 250 dispersion, amount Composition DICNATE1000W 3.2 3.2 3.2 3.2 3.2 (B) (note 3) adipic acid 0.25 0.25 0.25 0.250.25 0.25 0.25 3.25 3.25 dihydrazide TEXANOL (note 7) 15 15 15 15 15 1515 15 15 SN Deforamer 380 (note 14) 2 2 2 2 2 2 2 2 2 ADEKANOL UH-438(note 10) 2 2 2 2 2 2 2 2 2 sodium nitrite 0.5 0.5 0.5 0.5 0.5 0.5 0.50.5 0.5 Property Titanium White PVC 19 19 20 19 19 19 19 19 19 valuesanti-rusting pigment 3 3 3 PVC total pigment PVC 22 22 20 22 22 22 22 2222 Evaluation hardenability 82 83 83 87 85 88 86 87 86 thick appearance◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ gloss (60° G) 85 84 85 83 88 84 88 86 88 waterresistance ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ corrosion resistance ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯accelerated 8 8 8 8 8 8 8 8 8 weatherability points points points pointspoints points points points points Example 76 77 78 79 80 81 82 83 84Composition city water 40 40 40 40 40 40 40 40 40 (A) ethylene glycol 22 2 2 2 2 2 2 2 SURAOFF 72N (note 8) 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8NOPCOSANT K (note 9) 2 2 2 2 2 2 2 2 2 ADEKANOL UH-438 (note 10) 0.8 0.80.8 0.8 0.8 0.8 0.8 0.8 0.8 Titanium White 102 102 102.4 102.4 102.4102.4 102 102 102 JR-600A (note 11) SUNLITE SL-1500 (note 12) 10 10 1010 10 10 10 LF BOUSEI P-W-2 (note 13) 13 13 13 13 13 SN Defoamer 380(note 14) 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 aqueous resin I-9 I-10I-11 I-12 I-13 I-14 I-18 I-19 I-20 dispersion aqueous resin 253.2 253.2250 250 250 250 250 250 250 dispersion, amount Composition DICNATE 1000W3.2 3.2 3.2 3.2 3.2 3.2 3.2 (B) (note 3) adipic acid 3.25 3.25 0.25 0.250.25 0.25 0.25 0.25 0.25 dihydrazide TEXANOL(note 7) 15 15 15 15 15 1515 15 15 SN Deforamer 380 (note 14) 2 2 2 2 2 2 2 2 2 ADEKANOL UH-438(note 10) 2 2 2 2 2 2 2 2 2 sodium nitrite 0.5 0.5 0.5 0.5 0.5 0.5 0.50.5 0.5 Property Titanium White PVC 19 19 19 19 19 19 19 19 19 valuesanti-rusting pigment 3 3 3 3 3 PVC total pigment PVC 22 22 22 22 22 2222 22 22 Evaluation hardenability 90 88 85 81 82 86 85 83 84 thickappearance ◯ ◯ ⊚ ◯ ◯ ◯ ◯ ◯ ◯ gloss (60° G) 85 88 89 85 87 89 85 84 85water resistance ◯ ◯ ◯ ◯ ◯ ◯ ⊚ ⊚ ⊚ corrosion resistance ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯◯ accelerated 8 8 8 8 8 8 8 8 8 weatherability points points pointspoints points points points points points Example 85 86 87 88 89 90 9192 93 94 Composition city water 40 40 40 40 40 40 40 40 40 40 (A)ethylene glycol 2 2 2 2 2 2 2 2 2 2 SURAOFF 72N (note 8) 0.8 0.8 0.8 0.80.8 0.8 0.8 0.8 0.8 0.8 NOPCOSANT 2 2 2 2 2 2 2 2 2 2 K (note 9)ADEKANOL 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 UH-438 (note 10)Titanium 102 102 102 102 102 102 102 102 102 102 White JR-600A (note 11)SUNLITE 10 10 10 10 10 10 10 10 10 10 SL-1500 (note 12) LF BOUSEI 13 1313 13 13 13 P-W-2 (note 13) SN Defoamer 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.80.8 0.8 380 (note 14) aqueous resin I-21 I-22 I-23 I-24 I-25 I-26 I-27I-28 I-29 I-30 dispersion aqueous resin 250 250 250 250 250 250 250 250253 250 dispersion, amount Composition DICNATE 3.2 3.2 3.2 3.2 3.2 3.23.2 3.2 (B) 1000W (note 3) adipic acid 0.25 0.25 3.25 0.25 0.25 0.250.25 3.25 0.25 0.25 dihydrazide TEXANOL (note 7) 15 15 15 15 15 15 15 1515 15 SN Deforamer 2 2 2 2 2 2 2 2 2 2 380 (note 14) ADEKANOL 2 2 2 2 22 2 2 2 2 UH-438 (note 10) sodium nitrite 0.5 0.5 0.5 0.5 0.5 0.5 0.50.5 0.5 0.5 Property Titanium 19 19 20 19 19 19 19 19 19 19 values WhitePVC anti-rusting 3 3 3 3 3 3 pigment PVC total pigment 22 22 22 22 22 2222 22 22 22 PVC Evaluation hardenability 84 89 91 82 84 86 87 86 90 86thick ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ appearance gloss (60° G) 84 86 83 85 85 88 8889 87 88 water ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ◯ ◯ ◯ ◯ resistance corrosion ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯◯ ◯ resistance accelerated 8 8 10 9 9 10 10 10 10 8 weatherabilitypoints points points points points points points points points pointsExample Comparative example 95 96 97 98 99 100 9 10 11 12 Compositioncity water 40 40 40 40 40 40 40 40 40 40 (A) ethylene glycol 2 2 2 2 2 22 2 2 2 SURAOFF 72N (note 8) 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8NOPCOSANT 2 2 2 2 2 2 2 2 2 2 K (note 9) ADEKANOL 0.8 0.8 0.8 0.8 0.80.8 0.8 0.8 0.8 0.8 UH-438 (note 10) Titanium 102 102 102 102 102 102102 102 102 102.4 White JR-600A (note 11) SUNLITE 10 10 10 10 10 10 1010 10 10 SL-1500 (note 12) LF BOUSEI 13 13 13 13 13 13 13 13 13 13 P-W-2(note 13) SN Defoamer 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 380 (note14) aqueous resin I-31 I-32 I-33 I-34 I-35 I-36 I-15 I-16 I-17 I-37dispersion aqueous resin 250 250 250 250 250 250 250 250 200 250dispersion, amount Composition DICNATE 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.23.2 (B) 1000W (note3) adipic acid 0.25 5.25 5.25 5.25 5.25 0.25 0.250.25 0.25 0.25 dihydrazide TEXANOL (note 7) 15 15 15 15 15 15 15 15 1515 SN Deforamer 2 2 2 2 2 2 2 2 2 2 380 (note 14) ADEKANOL 2 2 2 2 2 2 22 2 2 UH-438 (note 10) sodium nitrite 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.50.5 0.5 Property Titanium 19 19 19 19 19 19 19 19 19 19 values White PVCanti-rusting 3 3 3 3 3 3 3 3 3 3 pigment PVC total pigment 22 22 22 2222 22 22 20 22 22 PVC Evaluation hardenability 88 78 78 75 77 82 60 8082 78 thick ◯ ◯ ◯ ◯ ◯ ◯ Δ ◯ ◯ Δ appearance gloss (60° G) 88 80 82 82 8185 87 74 78 54 water ⊚ ⊚ ◯ ◯ ◯ ◯ Δ Δ Δ Δ resistance corrosion ◯ ◯ ◯ ◯ ◯◯ Δ Δ Δ Δ resistance accelerated 10 8 8 10 8 8 8 8 8 7 weatherabilitypoints points points points points points points points points points(note 8)SURAOFF 72N: tradename, Tekeda Chemical Industries, Ltd., antiseptic(note 9)NOPCOSANT K: tradename, San Nopco Co., pigment dispersing agent(note 10)ADEKANOL UH-438: tradename, Adeka Co., thickener(note 11)Titaniun White JR-600A: tradename, TAYCA Corporation, titanium white,specific gravity = 4.1(note 12)SUNLITE SL-1500: tradename, Takehara Chemicals Co, calcium carbonate,specific gravity = 2.7(note 13)LF BOUSEI P-W-2: tradename, Kikuchi Color Co., zinc phosphate-basedanti-rusting agent, specific gravity = 3.5(note 14)SN Deforamer 380: tradename, San Nopco Co., defoaming agent(*3) Hardenability

Each of the water-based paint compositions was applied onto exfoliatepaper to a film thickness of 20μ and dried for a week. Then releasedcoating film was put in 20° C. acetone solvent and extracted for 24hours. The residual ratio (%) after the extraction was examined. Highervalues indicate better hardenability.

(*4) Thick Appearance

Each of the water-based paint compositions was applied onto glass sheetwith a 6-mil doctor blade and dried under the conditions of temperature,20° C. and relative humidity, 60%. The test-coated sheet samples werevisually evaluated after one day of the application:

-   -   ⊙ excellent thick appearance    -   ◯ good thick appearance    -   Δ poor thick appearance.        (*5) Gloss

Gloss at 60° of the test coated sheet samples as obtained in the samemanner as in above (*4) was measured. Higher values indicate bettergloss.

(*6) Water Resistance

Steel sheet (150×70×0.8 mm) meeting JIS K 5410 rating was degreased withxylene, and onto which each of the water-based paint compositions asdiluted with city water to about 70KU was applied with brush at anapplication rate of 150 g/m², followed by a week's drying at 20° C. andrelative humidity of 60%, to provide test panels. The test panels weregiven a water resistance test (96 hour's immersion) following JIS K5400-8.19. Conditions of the coated panel surfaces after the test wereevaluated according to the following standard.

-   -   ⊙: No cracking or peeling occurred and the gloss retention was        no less than 70%.    -   ◯: No cracking or peeling occurred and the gloss retention was        no less than 60%.    -   Δ: At least one of above criteria was not satisfied.        (*7) Corrosion Resistance

As the substrate material a steel sheet (150×70×0.8 mm) meeting JIS K5410 rating, which was degreased with xylene was used. Each of thewater-based paint compositions was diluted with city water to about 70KU, and applied onto the steel sheet with brush at an application rateof 100 g/m².

After a day's drying, second time application was conducted in themanner identical with the first time application, and dried for 7 daysunder the conditions of 20° C. and relative humidity of 60% to providetest panels. The test panels were subjected to 36 cycles of thecomposite cycle anti-corrosion test as specified by JIS K 5621, andthereafter the coated surfaces were evaluated according to the followingcriteria:

-   -   ◯: No rust found on the coated surface    -   Δ: Rust found on a part of the coated surface    -   x: Rust found over the whole of the coated surface.        (*8) Accelerated Weatherability

Test panels prepared in the same manner as those for the corrosion testwere irradiated for 1,000 hours according to the accleratedweatherability test as specified by JIS K 5400-9.8.1 (Sunshine carbonarc lamp system). Thereafter the coated surfaces were evaluated bydegree of chalking according to JIS K5400-9.6. Lower evaluation pointsindicate more advanced degree of chalking.

1. A process for producing an aqueous resin dispersion in which theaverage particle diameter of the dispersed resin is not more than 500nm, comprising finely dispersing a monomeric mixture (I) containing (A)fatty acid-modified polymerizable unsaturated monomer and (B) otherpolymerizable unsaturated monomer which is copolymerizable with themonomer (A) in an aqueous medium in such a manner that the dispersedparticles have an average particle diameter not more than 500 nm, andpolymerizing the resulting emulsified product.
 2. A process forproducing an aqueous resin dispersion in which the average particlediameter of the dispersed resin is not more than 500 nm, comprisingmini-emulsion polymerizing a monomeric mixture (I) containing (A) fattyacid-modified polymerizable unsaturated monomer and (B) otherpolymerizable unsaturated monomer which is copolymerizable with themonomer (A).
 3. A process as set forth in claim 1, in which the fattyacid-modified polymerizable unsaturated monomer (A) is a reactionproduct of fatty acid (a1) with epoxy-containing polymerizableunsaturated monomer (a2) or hydroxyl-containing polymerizableunsaturated monomer (a3).
 4. A process as set forth in claim 1, in whichthe composition of the other polymerizable unsaturated monomer (B) is soselected that the theoretical glass transition temperature of the(co)polymer of all the other polymerizable unsaturated monomer ormonomers constituting the monomer (B) falls within a range of 0-100° C.5. A process as set forth in claim 1, in which the other polymerizableunsaturated monomer (B) contains carboxyl-containing polymerizableunsaturated monomer (b1) at a ratio within a range of 0.1-5% by weight,based on the combined weight of the fatty acid modified polymerizableunsaturated monomer (A) and other polymerizable unsaturated monomer (B).6. A process as set forth in claim 1, in which the other polymerizableunsaturated monomer (B) contains polymerizable unsaturated monomer (b3)which contains straight chain or branched chain hydrocarbon group havingat least 6 carbon atoms, at a ratio within a range of 1-30% by weight,based on the combined weight of the fatty acid-modified polymerizableunsaturated monomer (A) and other polymerizable unsaturated monomer (B).7. A process as set forth in claim 1, in which the other polymerizableunsaturated monomer (B) comprises carboxyl-containing polymerizableunsaturated monomer (b1), polymerizable unsaturated monomer (b2) whichcontains a hydrocarbon group of at least 4 carbon atoms, andpolymerizable unsaturated monomer (b7) other than the fattyacid-modified polymerizable unsaturated monomer (A), above monomer (b 1)and monomer (b2), and in which the monomeric mixture (I) contains, basedon the combined weight of the monomers (A) and (B), 5-50% by weight ofmonomer (A), 0.1-5% by weight of monomer (b 1), 45-80% by weight ofmonomer (b2) and 0-49.9% by weight of the other polymerizableunsaturated monomer (b7), said polymerizable unsaturated monomer (b2)having a hydrocarbon group of at least 4 carbon atoms containingpolymerizable unsaturated monomer (b3) having a straight chain orbranched chain hydrocarbon group of at least 6 carbon atoms within arange of 1-30% by weight based on the combined weight of the monomers Aand B.
 8. A process as set forth in claim 1, in which the otherpolymerizable unsaturated monomer (B) comprises cycloalkyl-containingpolymerizable unsaturated monomer (b4).
 9. A process as set forth inclaim 1, in which the other polymerizable unsaturated monomer (B)comprises cycloalkyl-containing polymerizable unsaturated monomer (b4),aromatic vinyl monomer (b5), and other polymerizable unsaturated monomer(b8) other than above monomer (A), monomer (b4) and monomer (b5): and inwhich the monomeric mixture (I) contains, based on the combined weightof the monomers (A) and (B), 5-50% by weight of monomer (A), 1-70% byweight of monomer (b4), 1-50% by weight of monomer (b5), and 0-93% byweight of the other polymerizable unsaturated monomer (b8).
 10. Aprocess as set forth in claim 1, in which the other polymerizableunsaturated monomer (B) comprises carbonyl-containing polymerizableunsaturated monomer (b6).
 11. A process as set forth in claim 3, inwhich the fatty acid (a1) is selected from semi-drying oil fatty acidand nondrying oil fatty acid.
 12. A process as set forth in claim 1, inwhich the monomeric mixture (I) further comprises a compound whichcontains substantially no polymerizable unsaturated group.
 13. A processas set forth in claim 12, in which the compound containing substantiallyno polymerizable unsaturated group is at least one selected fromultraviolet absorber, ultraviolet stabilizer and metallic dryer. 14.Aqueous resin dispersions prepared by a process as set forth in claim 1.15. Aqueous resin compositions which comprise the aqueous resindispersions as set forth in claim
 14. 16. Aqueous resin compositions asset forth in claim 15, which further comprise hydrazine derivatives. 17.Aqueous resin compositions as set forth in claim 15, which form hardenedcoating film having a transmission haze value not higher than
 5. 18.Water-based paint compositions which comprise the aqueous resincompositions as set forth in claim
 15. 19. Water-based paintcompositions as set forth in claim 18, which further comprise titaniumwhite at a pigment volumetric concentration within a range of 5-25%. 20.Water-based paint compositions as set forth in claim 18, which furthercomprise phosphoric acid-derived pigment at a pigment volumetricconcentration within a range of 1-10%.
 21. Water-based paintcompositions as set forth in claim 18, which further comprise at leastone kind of compound selected from the group consisting of nitrous acidsalt, phytic acid salt, tannic acid salt and polyamine compound.
 22. Acoating film-forming method which comprises applying a water-based paintcomposition as set forth in claim 18 onto a substrate surface to becoated.
 23. A coating film-forming method as set forth in claim 22, inwhich the surface to be coated is that of an iron substrate or a coatedsurface of an iron substrate.
 24. Coated articles formed by the methodas set forth in claim 22.